Two devices cannot ping each other through WiFi
Solution 1:
Many wireless access points have "client isolation" enabled, which prohibits direct communication between connected devices. It's likely you just need to disable that.
Solution 2:
If you are looking for that, it is in Wireless -> Professional menu as "Set AP Isolated" and I had to set it to "Yes" and "Apply" and then back to "No" and "Apply" and now it works.